Fix PC Won't POST or No Display on Boot

Problem overview

Your computer turns on, fans spin, and lights illuminate, but your monitor displays “No Signal” and you never reach the BIOS screen or Windows. The system is failing the Power-On Self-Test (POST).

Common causes

• Unseated or incompatible RAM
• GPU power cables disconnected or GPU improperly seated
• Corrupted BIOS settings
• Failing power supply or dead motherboard

Solution 1: Check motherboard debug LEDs

1. Turn on the computer and inspect the motherboard near the 24-pin power connector.
2. Look for four small LEDs labeled BOOT, VGA, DRAM, and CPU.
3. Identify which LED stays solidly lit.
4. Address the specific component highlighted (e.g., if DRAM is lit, focus on the memory sticks).

Solution 2: Test with minimal hardware

1. Shut down the PC and turn off the power supply.
2. Remove all but one stick of RAM, placing it in the primary slot (usually A2).
3. Disconnect all storage drives, USB headers, and non-essential peripherals.
4. If your CPU has integrated graphics, remove the dedicated GPU and plug the monitor directly into the motherboard.
5. Attempt to boot. If it posts, add components back one by one until the system fails again to identify the culprit.

Solution 3: Clear the CMOS

1. Unplug the PC from the wall.
2. Locate the small, circular CR2032 battery on the motherboard and remove it carefully.
3. Wait 5 minutes to drain residual power.
4. Reinsert the battery and attempt to boot.
5. Alternatively, short the two pins labeled CLR_CMOS or JBAT1 with a screwdriver for 10 seconds.